Synthesis and properties of polyamides containing high contents of thioether units

Two kinds of monomers containing the thioether units 4,4′-thiodibenzoyl chloride (T-DC) and 4,4′-bis(4-chloroformylphenylthio)benzene (BPB-DC) were synthesized in two steps and were reacted with diamine-containing thioether (-S-) and sulfone units to prepare a polyamide containing high contents of thioether groups. The intrinsic viscosities of the polyamides were 0.81-0.93 dl/g. These polymers had good optical properties, including an optical transmittance of the aromatic polyamide film at 450 nm that was higher than 90%. Additionally, the high quantity of thioether units provided the polymers with high refractive indices of 1.710-1.716 and low birefringences of 0.007-0.009. These polyamides also had excellent thermal properties, with glass transition temperatures (Tg) of 230-246 °C and initial degradation temperatures (Td) of 477-473 °C. Finally, they showed improved solubility in polar aprotic solvents.